Siamotyrannus
| regnum = Animalia | phylum = Chordata | classis = Reptilia | superordo = Dinosauria | ordo = Saurischia | subordo = Theropoda | unranked_superfamilia = †Carnosauria | superfamilia = †Allosauroidea | familia = †Metriacanthosauridae | subfamilia = †Metriacanthosaurinae | genus = †''Siamotyrannus'' | genus_authority = Buffetaut, Suteethorn & Tong, 1996 | binomial = Siamotyrannus isanensis | binomial_authority = Buffetaut, Suteethorn & Tong, 1996 }} Siamotyrannus, name meaning "Siamese tyrant", is an extinct genus of theropod dinosaur which lived during the early Cretaceous period in what is now Thailand. Siamotyrannus was a large theropod, with estimates suggests an average length of 7 metres (23 ft) and a weight of around half a ton.Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press p. 91 Siamotyrannus is a large theropod. Buffetaut estimated its length at seven meters. In 2010, Gregory S. Paul estimated the length at six metres, the weight at half a ton. A possible autapomorphy, unique derived trait, is the possession of two vertical ridges on the ilium. The second and third sacrals are strongly transversely flattened. As evidenced by its name, it was originally thought to be a tyrannosauroid and even a tyrannosaurid, though due to lacking some of the primary tyrannosauroid synapomorphies that define the clade, its position here is not certain. Some analyses have categorized Siamotyrannus as a primitive carnosaur rather than a basal tyrannosauroid, and it has several features that may determine it to be an allosaurid or a sinraptorid. In 2012 Matthew Carrano e.a. found a position in the Metriacanthosauridae. Discovery In 1996, Eric Buffetaut, Varavudh Suteethorn and Haiyan Tong named and described the type species Siamotyrannus isanensis. The generic name is derived from the old Thai kingdom of Siam, and a Latinised Greek tyrannus, meaning "tyrant", in reference to a presumed membership of the Tyrannosauridae. The specific name is derived from Thai isan, "northeastern part", referring to the provenance from northeast Thailand. Classification As highlighted by its genus name, Siamotyrannus was originally identified as a tyrannosaur.Buffetaut, E., Suteethorn, V. and Tong, H. 1996. The earliest known tyrannosaur from the Lower Cretaceous of Thailand. Nature 381: 689-691 However, as it lacks some of the fundamental features of a tyrannosaur, its position in the group is not clear.Rauhut, Oliver W. M. Special Papers in Palaeontology: The Interrelationships and Evolution of Basal Theropod Dinosaurs (No. 69). The Palaeontological Association: 2003 Some scientists refer to Siamotyrannus as a primitive carnosaur, rather than a basal tyrannosauroid, as it possesses several features that occur in some allosaurids and sinraptorids.Holtz, Thomas R. et al. (2004). "Basal Tetanurae." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. p. 101 ISBN 0-520-24209-2 In 2012, Matthew Carrano e.a. found a position in the MetriacanthosauridaeCarrano, M. T.; Benson, R.B.J.; Sampson, S.D., 2012, "The phylogeny of Tetanurae (Dinosauria: Theropoda)". Journal of Systematic Palaeontology 10(2): 211–300 Gallery Siamotyrannus/Gallery References Category:Carnivores Category:Cretaceous metriacanthosaurids Category:Metriacanthosaurids Category:Extinct animals of Thailand Category:Fossil taxa described in 1996 Category:Dinosaurs of Asia Category:Dinosaur King creatures Category:Tyrannosaurs Category:Extinct animals of Asia Category:Medium-sized carnivores Category:Predators